Determining exact location within a field

[Dan Soneson]

Does anyone know of a way to find the location of a specific spot 
within a text field? I am interested in developing a module that will 
allow me to construct a fill-in-the-blank activity. My thought is to 
construct a text in a field and mark the words that I want to replace 
in some way (precede them with a special character). Then I want to 
construct a button with a script that finds the words with this 
character in the text and replaces them with a space. Over this space I 
want to create a field into which users can enter the missing word. It 
would be nice to automate this process and to be able to know exactly 
where to place the new field, how large to make it, etc. But I cannot 
figure out the placement issue.

Any suggestions appreciated.

Dan